(1) Field of the Invention
The invention relates to data processing and analysis of manufacturing data, and more particularly, to a method and an apparatus for an improved graphical depiction of work-in-progress and production moves data for use in integrated circuit manufacturing management.
(2) Description of the Prior Art
Efficient management of a integrated circuit manufacturing plant is a difficult technical and managerial challenge. Meeting customer delivery dates, maintaining a balanced manufacturing line, working around equipment maintenance and repair, and responding to frequently changing customer orders are among the problems facing the manufacturing manager. To properly manage the production facility, manufacturing managers rely on data reports that provide ‘snapshots’ of the status of the wafer fab.
Referring now to FIG. 1, an example of a prior art data report is illustrated. A Key Stage Report 10, or KSR, is a summary report that a manufacturing supervisor uses to analyze the fabrication facility or a cell within such a facility. A KSR 10 is generated from the manufacturing information system (MIS) database for the fabrication facility. The KSR 10 shown provides summary information for each key stage in the plant. Key stages in the production process are designated by stage ID labels. For example, the first key stage in the process is the wafer start or WF1_START stage.
Several parameters are provided for each key stage. In this example KSR 10, the work-in-progress (WIP) is given for the WF1_START stage as 226 wafers. The WIP for each stage is provided, along with several other parameters, such as the held WIP (HWIP), the banked WIP (BANK), and the cumulative WIP (CUMWP). Production line supervisors use a KSR 10 in this form to analyze the balance of the production line. The supervisors make decisions, such as how many production lots to release on to the floor or where to focus manpower, based on their analysis of the KSR. Maintaining a balanced production line is a critical strategy in achieving optimum equipment utilization, on- time delivery, and minimum costs.
The KSR 10 shown in FIG. 1 has a distinct disadvantage because it is a text-only report. It is difficult for the line supervisor or the production operator to have an intuitive feeling as to where the production imbalance lies. Unless the person analyzing the textual data has a wealth of experience, it is likely that the large listing of data will not be very useful in the decision making process.
Several prior art inventions disclose manufacturing decision making systems and database tools. U.S. Pat. No. 5,612,886 to Weng discloses a manufacturing control system using a computer control of workflow. WIP is sorted by priority and by queue time. A dynamic dispatch ranking is calculated and the highest priority production stage is selected automatically. U.S. Pat. No. 5,818,716 to Chin et al teaches a dispatching algorithm for use in integrated circuit manufacture. A required turn rate (RTR) metric is calculated for each wafer lot. The RTR is then used for automatic dispatching of lots to thereby maximize throughput and equipment utilization. U.S. Pat. No. 5,559,710 to Shahraray et al discloses a system and a method to schedule the release of production lots into a factory. A continuity index (CI) is defined for each wafer lot. A factory profile curve of optimum CI value is established. The dispatch of lots is automatically controlled to force the current CI value towards the optimum CI curve. U.S. Pat. No. 5,889,673 to Pan et al teaches a system and a method to automatically and to dynamically dispatch lots in an IC manufacturing environment. A stage achievement rate (SAR) is calculated and used in the automatic dispatch selection algorithm. U.S. Pat. No. 5,841,667 to Yang et al discloses a system and a method to automatically dispatch lots to available machine processes. The average process time, the average number of lots per batch in the succeeding process, and the allowable lots metrics are used in the dispatch algorithm. U.S. Pat. No. 5,768,133 to Chen et al teaches a system and a method for interactive data processing in an IC manufacturing plant. The graphical user interface (GUI) displays data, including WIP data.